Avalanche Forecast

Elevated snow levels, increasing moderate to heavy precipitation Monday afternoon, and strong crest-level winds will all combine to create very dangerous avalanche conditions on Monday. The added weight of rain or heavy wet snow will stress the upper snowpack. 

Travel in avalanche terrain is not recommended on Monday so avoid terrain where avalanches may start, run, and stop.

Both dry and wet snow avalanches are anticipated to become widespread as the storm intensifies Monday afternoon. The avalanche danger will be particularly severe in the Cascades East-North zone where the storm will arrive earlier in the day leading to greater loading of snow and water during the daylight hours.

These avalanches may be large to very large and will be found on all aspects as recent winds have redistributed recent snow to a variety of depths across the terrain. Wind slabs will also be actively building, particularly on NW-SE terrain.

Avalanches releasing to the 1/16 crust layer may run long distances. 

A storm system on Saturday brought significant snow and wind during the daytime hours. Snow continued in many locations Saturday night with the passage of a warm front on Sunday morning. Snow totals from Saturday morning through Sunday afternoon are in the 10-15" range in the north with the snow falling at increasing density, resulting in an upside-down storm slab layer within the upper snowpack.

The recent storm layers are unstable as light rain was seen on Sunday morning up to the top of the treeline band.

Winds throughout the storm cycle have redistributed snow forming sensitive wind slabs on a variety of aspects.

The lower elevation rain should help the treeline rain band to settle and start to stabilize slightly while the recent warmer temperatures should help the older wind slabs from Saturday and earlier to continue healing.

Estimated settled snow depths above the 1/16 crust are now 30+ inches in northern areas.

Some recent observations from around the east slopes central and north found buried surface hoar above the 1/16 crust. There is still quite a bit of uncertainty about the distribution of this layer in these zones. Extra caution should be taken when traveling in areas further east of the crest or in areas where less snow has been received. Snow profiles and snowpack tests are the only means to identify and locate this layer. 

Observations

North

On Friday, North Cascades Mountain Guides found the upper snowpack generally gaining strength. Some snowpack test failed below the 1/16 crust.

On Thursday and Friday, NCH observed evidence of several recent wind slabs that had released in steep terrain above treeline in the Washington Pass area. Away from wind affected terrain and in several snowpits, a generally stable and right-side-up upper snowpack was noted. 

NWAC received a second-hand report of a large skier-triggered avalanche on west-facing slope (likely near treeline) on Abernathy Peak in the upper Twisp River drainage. The avalanche propagated widely and was suspected to have failed on the 1/16 crust.

Central

On Sunday, NCMG was on Dirtyface Mountain and reported a deep and very upside-down upper snowpack that was not showing the anticipated reactivity given the structure. Buried wind slabs were present, but unreactive near ridge crest.

Mission Ridge Ski Patrol reported very high winds and active wind loading on N-NE slopes Saturday with very reactive wind slabs producing 4-30" crowns. In wind sheltered location soft surface snow was found. Surface hoar has been observed in the area on the 1/16 crust.

A public observation from Wednesday in the Blewett Pass area identified basal facets at the bottom of the snowpack and surface hoar above the most recent crust. Snow cover was still regionally low in this area.

Buried surface hoar was found in the Icicle Creek drainage over the 1/16 crust over a week ago up to 6800 ft. 

South

No recent observations